Project 1 concentrates on the role of the transcription factor CREB in mediating the long-term actions of opiates and cocaine. The major focus is the NAc (nucleus accumbens). We have considerable evidence that increased CREB function in this brain region, which occurs in response to chronic opiate or stimulant exposure, represents one mechanism of drug tolerance and dependence. Thus, CREB activation in the NAc decreases an animal's sensitivity to subsequent drug exposure, and induces a negative emotional state, which suggests that it may contribute to aversive symptoms during drug withdrawal. We will further characterize the CREB behavioral phenotype in the NAc in additional behavioral models and by use of more advanced tools which selectively knockout CREB from this brain region. We will also establish the behavioral phenotype of several other CREB family proteins, which we have shown recently are also regulated in the NAc by drugs of abuse and subserve very different functions in the NAc. Related studies will characterize target genes through which CREB produces this behavioral phenotype in the NAc. The genes encoding the opioid peptide dynorphin, the AMPA glutamate receptor subunit GluR1, adenylyl cyclase type 8, and BDNF (brain-derived neurotrophic factor) are examples of such targets of CREB that will be examined in this Project, as will additional targets identified with DNA expression arrays and ChIP on chip (chromatin mmunoprecipitation x promoter) arrays. ChIP will also be used to characterize the molecular mechanisms by which CREB, at the level of chromatin remodeling, regulates its target genes. In addition, the Project will carry out a smaller number of highly targeted investigations of the role played by CREB in the VTA (ventral tegmental area) and LC (locus coeruleus) in mediating long-term drug action in these regions. Our studies of the LC, in particular, continue to provide novel insight into the molecular and cellular basis of drug action, which informs our studies of the VTA-NAc reward circuit. CREB function is one of the major themes of this PPG. All of the subsequent Projects of this Grant represent, in part, extensions of our central hypothesis that CREB in the VTA-NAc is a key regulator of drug reward and addiction. Subsequent Projects extend this theme by characterizing the influence of CREB, and related transcriptional mechanisms (i.e., AFosB), on the neurophysiology of VTA and NAc neurons (Project 2), on the detailed molecular mechanisms of gene regulation including modifications in chromatin structure n the VTA-NAc (Project 3), and by further establishing the complex behavioral phenotype mediated by CREB and related transcriptional mechanisms in drug reinforcement and craving (Project 4).